linux-kernel - Re: [PATCH 38/44] kdbus: Fix error path in kdbus_user

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Date:	Thu, 8 Oct 2015 17:06:57 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	Sergei Zviagintsev <sergei@...v.net>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 38/44] kdbus: Fix error path in kdbus_user_lookup()

Hi

On Thu, Oct 8, 2015 at 1:32 PM, Sergei Zviagintsev <sergei@...v.net> wrote:
> If idr_alloc() fails, we shouldn't call idr_remove() as latter produces
> warning when called on non-allocated ids. Split cleanup code into three
> parts for differrent cleanup scenarios before and after idr_alloc().
>
> Signed-off-by: Sergei Zviagintsev <sergei@...v.net>
> ---
>  ipc/kdbus/domain.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/ipc/kdbus/domain.c b/ipc/kdbus/domain.c
> index ac9f760c150d..31cd09fb572f 100644
> --- a/ipc/kdbus/domain.c
> +++ b/ipc/kdbus/domain.c
> @@ -208,7 +208,7 @@ struct kdbus_user *kdbus_user_lookup(struct kdbus_domain *domain, kuid_t uid)
>         u = kzalloc(sizeof(*u), GFP_KERNEL);
>         if (!u) {
>                 ret = -ENOMEM;
> -               goto exit;
> +               goto exit_unlock;
>         }
>
>         kref_init(&u->kref);
> @@ -225,7 +225,7 @@ struct kdbus_user *kdbus_user_lookup(struct kdbus_domain *domain, kuid_t uid)
>                         ret = idr_alloc(&domain->user_idr, u, __kuid_val(uid),
>                                         __kuid_val(uid) + 1, GFP_KERNEL);
>                         if (ret < 0)
> -                               goto exit;
> +                               goto exit_free;
>                 }
>         }
>
> @@ -235,19 +235,19 @@ struct kdbus_user *kdbus_user_lookup(struct kdbus_domain *domain, kuid_t uid)
>          */
>         ret = ida_simple_get(&domain->user_ida, 1, 0, GFP_KERNEL);
>         if (ret < 0)
> -               goto exit;
> +               goto exit_idr;
>

Why not simply assign "u->uid = uid;" _after_ doing the idr operations?

Thanks
David

>         u->id = ret;
>         mutex_unlock(&domain->lock);
>         return u;
>
> -exit:
> -       if (u) {
> -               if (uid_valid(u->uid))
> -                       idr_remove(&domain->user_idr, __kuid_val(u->uid));
> -               kdbus_domain_unref(u->domain);
> -               kfree(u);
> -       }
> +exit_idr:
> +       if (uid_valid(u->uid))
> +               idr_remove(&domain->user_idr, __kuid_val(u->uid));
> +exit_free:
> +       kdbus_domain_unref(u->domain);
> +       kfree(u);
> +exit_unlock:
>         mutex_unlock(&domain->lock);
>         return ERR_PTR(ret);
>  }
> --
> 1.8.3.1
>
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